[Zope] filling ZClass addForm with default values?

In addition to defining the various names and types of my ZClass's properties in its property sheet, I have also set a few default values. The question is: what is the easiest way of getting these default values to show up in the class's addForm? Is it necessary to use a fully qualified path from the ZODB root, e.g., something like <dtml-var "Control_Panel.Products.MyProduct.MyClass.propertysheets.common.Basic.prop1"

Generall speaking, I seem to have problems referring to data in the Products hierarchy. As always, any help is much appreciated. Cheers, Darran.